Clear glass composition

ABSTRACT

Glass is provided so as to have high visible transmission and/or fairly clear or neutral color. In certain example embodiments of making glass according to examples of the invention, the glass batch may include a base glass (e.g., soda lime silica base glass) and, in addition, by weight percentage:  
                                           total iron (expressed as Fe 2 O 3 ):    0.01 to 0.30%         erbium oxide (e.g., Er 2 O 3 ):    0.01 to 0.30%         cerium oxide (e.g., CeO 2 ):   0.005 to 0.30%.                                
 
     Optionally, neodymium oxide (e.g., Nd 2 O 3 ) may also be provided in the glass in certain example embodiments. In other embodiments, the cerium oxide may be replaced with or supplemented by NaNO 3  or some other nitrate(s) as an oxidizer.

[0001] This invention relates to glass compositions and methods ofmaking the same. More particularly, this invention relates to glasshaving high light transmittance in the visible range and/or fairlyneutral color. Such glass compositions are thus useful, for example, inarchitectural windows, patterned glass applications, solar cells, and/orautomotive windows.

BACKGROUND OF THE INVENTION

[0002] Glass that is fairly clear in color and highly transmissive tovisible light (e.g., at least 75% transmissive, or even more preferablyat least 80% transmissive) is sometimes desirable. One way of achievingsuch as glass is to use very pure base glass materials (e.g.,substantially free of colorants such as iron). However, base materialswith a high degree of purity are expensive and thus not always desirableand/or convenient. In other words, for example, the removal of iron fromglass raw materials has certain practical and/or economical limits.

[0003] As can be appreciated from the above, glass raw materials (e.g.,silica, soda ash, dolomite, and/or limestone) typically include certainimpurities such as iron. The total amount of iron present is expressedherein in terms of Fe₂O₃ in accordance with standard practice. However,typically, not all iron is in the from of Fe₂O₃. Instead, iron isusually present in both the ferrous state (Fe²⁺; expressed herein asFeO, even though all ferrous state iron in the glass may not be in theform of FeO) and the ferric state (Fe³⁺). Iron in the ferrous state(Fe²⁺; FeO) is a blue-green colorant, while iron in the ferric state(Fe³⁺) is a yellow-green colorant. The blue-green colorant of ferrousiron (Fe²⁺; FeO) is of particular concern when seeking to achieve afairly clear or neutral colored glass, since as a strong colorant itintroduces significant color into the glass. While iron in the ferricstate (Fe³⁺) is also a colorant, it is of less concern when seeking toachieve a glass fairly clear in color since iron in the ferric statetends to be weaker as a colorant than its ferrous state counterpart.

[0004] In view of the above, it is apparent that there exists a need inthe art for a new glass composition which enables a glass to have fairlyclear color and/or high visible transmission, without having to resortto extremely pure (i.e., free of iron) glass raw materials.

SUMMARY OF THE INVENTION

[0005] An object of this invention is to provide a glass that has fairlyclear color and/or high visible transmission.

[0006] Another object of this invention is to provide a glass having avisible transmission of at least 75% (more preferably at least 80%, andmost preferably at least 85%), wherein in making the glass a batchtherefor includes a base glass (e.g., soda lime silica glass) and inaddition comprising (or consisting essentially of in certainembodiments), by weight percentage: total iron (expressed as Fe₂O₃): 0.01 to 0.30% erbium oxide (e.g., Er₂O₃):  0.01 to 0.30% cerium oxide(e.g., CeO_(2):) 0.005 to 0.30%.

[0007] Optionally, other colorants such as neodymium oxide (e.g., Nd₂O₃)may also be provided in certain example embodiments. While cerium oxideis preferred in many embodiments, its presence is not a requirement. Inother embodiments of this invention, the cerium oxide (e.g., CeO₂) inthe glass batch may be either replaced or supplemented by sodium nitrate(NaNO₃) as an oxidizer.

[0008] Another object of this invention is to fulfill one or more of theabove-listed objects and/or needs.

[0009] Certain example embodiments of the invention fulfill one or moreof the above-listed objects and/or needs by providing a method of makingglass, the method comprising: providing a glass batch comprising:Ingredient wt. % SiO₂ 67-75% Na₂O 10-20% CaO  5-15% MgO  0-5% Al₂O₃ 0-5% K₂O  0-5% total iron (expressed as Fe₂O₃)  0.01 to 0.30% erbiumoxide  0.01 to 0.30% cerium oxide and/or a nitrate 0.005 to 2.0%neodymium oxide    0 to 0.15%

[0010] melting the batch and forming a resulting glass that has visibletransmission of at least 75%, a transmissive a* color value of −1.0 to+1.0, and a transmissive b* color value of −1.0 to +1.5.

[0011] Certain other example embodiments of this invention fulfill oneor more of the above-listed objects and/or needs by providing a glasscomprising: total iron (expressed as Fe₂O₃)  0.01 to 0.30% erbium oxide 0.01 to 0.30% cerium oxide 0.005 to 0.30%.

[0012] Certain other example embodiments of this invention fulfill oneor more of the above-listed objects and/or needs by providing a methodof making glass, the method comprising providing a glass batchcomprising: total iron (expressed as Fe₂O₃):  0.01 to 0.30% erbiumoxide:  0.01 to 0.30% cerium oxide and/or a nitrate: 0.005 to 2.0%, andusing the glass batch to make glass.

[0013] Certain other example embodiment of this invention fulfill one ormore of the above-listed objects and/or needs by providing a glasscomprising: total iron (expressed as Fe₂O₃) 0.01 to 0.30%, and erbiumoxide 0.01 to 0.30%.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THIS INVENTION

[0014] Glasses according to different embodiments of this invention maybe used, for example, in the automotive industry (e.g., windshields,backlites, side windows, etc.), in architectural applications, forpatterned glass applications, solar cell applications, and/or in othersuitable applications.

[0015] Certain glasses according to this invention utilizesoda-lime-silica flat glass as their base composition/glass. In additionto base composition/glass, a unique colorant portion is provided inorder to achieve a glass that is fairly clear in color and/or has a highvisible transmission. An exemplary soda-lime-silica base glass accordingto certain embodiments of this invention, on a weight percentage basis,includes the following basic ingredients: TABLE 1 EXAMPLE BASE GLASSIngredient Wt. % SiO₂ 67-75% Na₂O 10-20% CaO  5-15% MgO  0-5% Al₂O₃ 0-5% K₂O  0-5% BaO  0-1%

[0016] Other minor ingredients, including various conventional refiningaids, such as SO₃, carbon, and the like may also be included in the baseglass. In certain embodiments, for example, glass herein may be madefrom batch raw materials silica sand, soda ash, dolomite, limestone,with the use of salt cake (SO₃) and/or Epsom salts (e.g., about a 1:1combination of both) as refining agents. Preferably, soda-lime-silicabased glasses herein include by weight from about 10-15% Na₂O and fromabout 6-12% CaO. While a soda-lime-silica base glass set forth above ispreferred in certain embodiments of this invention, this invention isnot so limited. Thus, other base glasses (e.g., borosilicate glass) mayinstead be employed in alternative embodiments of this invention.

[0017] In addition to the base glass (e.g., see Table 1 above), inmaking glass according to the instant invention the glass batch includesmaterials (including colorants and/or oxidizers) which cause theresulting glass to be fairly neutral in color and/or have a high visiblelight transmission. These materials may either be present in the rawmaterials (e.g., small amounts of iron), or may be added to the baseglass materials in the batch (e.g., cerium, erbium, etc.). In certainpreferred embodiments, the resulting glass has visible transmission ofat least 75%, more preferably at least 80%, and most preferably at least85%.

[0018] In certain embodiments of this invention, in addition to the baseglass, the glass batch includes materials as set forth in Table 2 below(in terms of weight percentage of the total glass composition): TABLE 2EXAMPLE GLASS BATCH OF FIRST EMBODIMENT General More Most Ingredient(Wt. %) Preferred Preferred total iron (expressed  0.01-0.30% 0.02-0.20%0.03-0.15% as Fe₂O₃): erbium oxide (e.g., Er₂O₃):  0.01-0.30% 0.02-0.20%0.03-0.13% cerium oxide (e.g., CeO₂): 0.005-0.30% 0.01-0.18% 0.03-0.12%

[0019] The batch is melted and glass formed using the known floatprocess. Optionally, in certain example embodiments of the invention,neodymium oxide (e.g., Nd₂O₃) may be added to the batch, as exemplifiedbelow in Table 3 according to a second example embodiment of thisinvention (the material listed in Table 3 are in addition to the baseglass described above). TABLE 3 EXAMPLE GLASS BATCH OF SECOND EMBODIMENTGeneral More Most Ingredient (Wt. %) Preferred Preferred total iron(expressed as  0.01-0.30%  0.02-0.20%  0.03-0.15% Fe₂O₃): erbium oxide 0.01-0.30%  0.02-0.20%  0.03-0.13% (e.g., Er₂O₃): cerium oxide0.005-0.30%  0.01-0.18%  0.03-0.12% (e.g., CeO₂): neodymium oxide0.005-0.15% 0.010-0.050% 0.010-0.030% (e.g., Nd₂O₃):

[0020] In certain embodiments of this invention (e.g., first and/orsecond embodiments above), the colorant portion is substantially free ofother colorants (other than potentially trace amounts). However, itshould be appreciated that amounts of other materials (e.g., refiningaids, melting aids, colorants and/or impurities) may be present in theglass in certain other embodiments of this invention without taking awayfrom the purpose(s) and/or goal(s) of the instant invention. It is notedthat while the presence of cerium oxide is preferred in many embodimentsof this invention, it is not required in all embodiments. Moreover, itis possible to use little or no Er in certain embodiments of thisinvention.

[0021] In other embodiments of this invention, the cerium oxide (e.g.,CeO₂) may be either replaced or supplemented by NaNO₃ in the glassbatch; see the third, fourth and fifth embodiments below (the batchmaterials in Tables 4-6 below are in addition to the base class rawmaterials described above). TABLE 4 EXAMPLE GLASS BATCH OF THIRDEMBODIMENT General More Most Ingredient (Wt. %) Preferred Preferredtotal iron (expressed as 0.01-0.30% 0.02-0.20% 0.03-0.15% Fe₂O₃): erbiumoxide (e.g., Er₂O₃): 0.01-0.30% 0.02-0.20% 0.03-0.13% sodium nitrate(NaNO₃):  0.1-2.0%  0.2-1.5%  0.3-1.2%

[0022] TABLE 5 EXAMPLE GLASS BATCH OF FOURTH EMBODIMENT General MoreMost Ingredient (Wt. %) Preferred Preferred total iron (expressed as 0.01-0.30%  0.02-0.20%  0.03-0.15% Fe₂O₃): erbium oxide  0.01-0.30% 0.02-0.20%  0.03-0.13% (e.g., Er₂O₃): sodium nitrate  0.1-2.0% 0.2-1.5%  0.3-1.2% (NaNO₃): neodymium oxide 0.005-0.15% 0.010-0.050%0.010-0.030% (e.g., Nd₂O₃):

[0023] TABLE 6 EXAMPLE GLASS BATCH OF FIFTH EMBODIMENT General More MostIngredient (Wt. %) Preferred Preferred total iron (expressed as0.01-0.30% 0.02-0.20% 0.03-0.15% Fe₂O₃): erbium oxide (e.g., Er₂O₃):0.01-0.30% 0.02-0.20% 0.03-0.13% cerium oxide (e.g., CeO₂):   0-0.30%  0-0.18%   0-0.12% sodium nitrate (NaNO₃):   0-2.0%  0.2-1.5%  0.3-1.2%

[0024] In the fifth embodiment (see Table 6 above), cerium oxide (e.g.,CeO₂) and sodium nitrate (NaNO₃) may be combined as oxidizers, so as tocause the effects of equations (1) and (2) below. Accordingly, one orboth of cerium oxide and/or sodium nitrate may be provided in this fifthembodiment.

[0025] It is noted that in certain embodiments herein, the amount oftotal iron may even be less than 0.10%.

[0026] The above batches are melted and the float process used to formglass (e.g., soda lime silica glass) in a known manner.

[0027] The total amount of iron present in the glass batch and in theresulting glass, i.e., in the colorant portion thereof, is expressedherein in terms of Fe₂O₃ in accordance with standard practice. This,however, does not imply that all iron is actually in the form of Fe₂O₃(see discussion above in this regard). Likewise, the amount of iron inthe ferrous state (Fe⁺²) is reported herein as FeO, even though allferrous state iron in the glass batch or glass may not be in the form ofFeO. As mentioned above, iron in the ferrous state (Fe²⁺; FeO) is ablue-green colorant, while iron in the ferric state (Fe³⁺) is ayellow-green colorant; and the blue-green colorant of ferrous iron is ofparticular concern, since as a strong colorant it introduces significantcolor into the glass which can sometimes be undesirable when seeking toachieve a neutral or clear color.

[0028] According to certain example embodiments of this invention, thepresence of cerium oxide (e.g., CeO₂) as an oxidizer in the glass batchacts as a chemical decolorizer since during melting of the glass batchit causes iron in the ferrous state (Fe²⁺; FeO) to oxidize to the ferricstate (Fe³⁺) as illustrated by the following equation:

Fe²⁺+Ce⁴⁺=Fe³⁺+Ce³⁺  (1)

[0029] Equation (1) shows that the presence of cerium oxide in the glassbatch causes an amount of the strong blue-green colorant of ferrous iron(Fe²⁺; FeO) to oxidize into the weaker yellow-green ferric iron colorant(Fe³⁺) during the glass melt (note: some ferrous state iron will usuallyremain in the resulting glass, as potentially may some Ce⁴⁺).Accordingly, a significant portion of the CeO₂ added to the originalglass batch prior to the melt is transformed during the melt into Ce₂O₃which is present in the resulting glass. The aforesaid oxidation of theiron tends to reduce coloration of the glass, and does not significantlydecrease visible light transmission of the resulting glass (in certaininstances, this may even causes visible transmission to increase).However, those of skill in the art will appreciate that there stillexists significant coloration in the glass due to the ferric iron ifonly the iron and cerium oxide are provided. In other words, it has beenfound that adding cerium oxide to only iron containing glass is notsufficient to achieve a desired fairly clear or neutral color.

[0030] It is noted that, like Fe₂O₃, the phrase “cerium oxide” as usedherein refers to total cerium oxide (i.e., including cerium oxide inboth the Ce⁴⁺ and Ce³⁺ states).

[0031] As mentioned above, the cerium oxide may be replaced by, orsupplemented with, sodium nitrate in certain example embodiments of thisinvention. In embodiments where sodium nitrate (NaNO₃) is provided inthe glass (e.g., see Tables 3-5 above), it functions in a manner similarto cerium oxide as shown in the below equation (but note the potentialfor oxygen bubbles). In particular, like cerium oxide, sodium nitratecan be added to the glass batch as an oxidizer to cause an amount of thestrong blue-green colorant of ferrous iron (Fe²⁺; FeO) to oxidize intothe weaker yellow-green ferric iron colorant (Fe³⁺) during the glassmelt (note: some ferrous state iron will usually remain in the resultingglass):

Fe²⁺NO₃=Fe³⁺+NO₂+½O₂   (2)

[0032] Those skilled in the art will recognize that the most of thenitrate (e.g., sodium nitrate) added to the glass batch decomposesduring the melt so that some burns off as NO_(x) while other parts of itend up in the glass as Na₂O. While sodium nitrate (NaNO₃) is utilized asan oxidizer in Tables 4-6 above, the instant invention is not solimited. For example, other nitrates (e.g., potassium nitrate KNO₃, orany other suitable nitrate) may be used instead of or in addition tosodium nitrate in alternative embodiments of this invention.

[0033] In order to compensate for the color caused by the ferric ironresulting from the addition of the cerium oxide and/or sodium nitrate,it has been found that adding erbium oxide (e.g., Er₂O₃ or any othersuitable stoichiometric form) and/or neodymium oxide (e.g., Nd₂O₃ of anyother suitable stoichiometric form) causes the color of the resultingglass to become more clear (i.e., more neutral as the a* and/or b* colorvalue(s) move(s) toward neutral 0). Erbium oxide acts as a pinkcolorant, while neodymium oxide acts as a purple colorant. One or bothof Er and/or Nd apparently acts to physically compensate for the ironcolor, thereby making the color of the glass more neutral which isdesirable in certain embodiments of this invention, while enabling theglass to still have high visible transmission.

[0034] It will be appreciated by those skilled in the art that theaddition of cerium oxide and/or sodium nitrate (see equations (1) and(2) above) results in a glass with a lower “redox” value (i.e., lessiron in the ferrous state FeO). In this regard, the proportion of thetotal iron in the ferrous state (FeO) is used to determine the redoxstate of the glass, and redox is expressed as the ratio FeO/Fe₂O₃, whichis the weight percentage (%) of iron in the ferrous state (FeO) dividedby the weight percentage (%) of total iron (expressed as Fe₂O₃) in theresulting glass. Due to the presence of the cerium oxide and/or sodiumnitrate, the redox of glass according to certain example embodiments ofthis invention is rather low; in particular, glass according to certainexample embodiments of this invention may have a redox value (i.e.,FeO/Fe₂O₃) of less than or equal to 0.25, more preferably less than orequal to 0.20; even more preferably less than or equal to 0.15, and mostpreferably less than or equal to 0.13. Moreover, resulting glassaccording to certain example embodiments of this invention may includeiron in the ferrous state (FeO) in an amount (wt. %) of less than orequal to 0.020%, more preferably less than or equal to 0.015%, and mostpreferably less than or equal to 0.011%.

[0035] It is noted that glass according to this invention is often madevia the known float process in which a tin bath is utilized. It willthus be appreciated by those skilled in the art that as a result offorming the glass on molten tin in certain exemplary embodiments, smallamounts of tin or tin oxide may migrate into surface areas of the glasson the side that was in contact with the tin bath during manufacture(i.e., typically, float glass may have a tin oxide concentration of0.05% or more (wt.) in the first few microns below the surface that wasin contact with the tin bath).

[0036] In view of the above, glasses according to certain exampleembodiments of this invention achieve a neutral or substantially clearcolor and/or high visible transmission. In certain embodiments,resulting glasses according to certain example embodiments of thisinvention may be characterized by one or more of the followingtransmissive optical or color characteristics when measured at athickness of from about 1 mm-6 mm (most preferably a thickness of about0.219 inches; this is a non-limiting thickness used for purposes ofreference only) (Lta is visible transmission %): TABLE 7 CHARACTERISTICSOF CERTAIN EXAMPLE EMBODIMENTS Characteristic General More PreferredMost Preferred Lta (Ill. C, 2 deg.):   >=75%   >=80%   >=85% % UV (Ill.C. 2 deg.):   <=85%   <=80%   <=75% % TS (Ill. C. 2 deg.):   <=90%  <=87%   <=85% % FeO (wt. %): <=0.020% <=0.015% <=0.011% L* (Ill. D65,10 deg.): 90-100 n/a n/a a* (Ill. D65, 10 deg.): −1.0 to +1.0 −0.60 to+0.60 −0.30 to +0.50 b* (Ill. D65, 10 deg.): −1.0 to +1.5 −0.70 to +1.0−0.30 to +0.40

[0037] As can be seen from Table 7 above, glasses of certain embodimentsof this invention achieve desired features of fairly clear color and/orhigh visible transmission, while not requiring iron to be eliminatedfrom the glass composition. This may be achieved through the provisionof the unique material combinations described herein.

EXAMPLES

[0038] Example glasses of this invention may be made from batchingredients using well known glass melting and refining techniques. Thefollowing approximate base glass batch was used for the Examples herein(note: the below-listed ingredients in the batch will add up to 100% byweight once oxides thereof are accounted for; thus, they need not add upto one hundred as raw materials): Batch Ingredient for Base Glass Partsby Wt. sand 71.5 soda ash 23.7 dolomite 18.32 limestone 6.1 Epsom salt0.9

[0039] In addition to the base glass batch materials above, thematerials set forth below were present in the original batch(es) for theExamples (compound amounts given in wt. %). It is noted that Examples1-8 are according to different example embodiments of this invention,while CA, CB and CC are Comparative Examples provided for purposes ofcomparison with Examples 1-8. In particular, Comparative Example A (CA)should be compared to Examples 1-3 of this invention since they all havethe same amount of total iron, while Comparative Example B (CB) shouldbe compared to Examples 4-5 of this invention since they all have thesame total iron amount, and Comparative Example C (CC) should becompared to Examples 6-8 of this invention since they all have the sameamount of total iron. BATCH MATERIALS IN EXAMPLES 1-8 (IN ADDITION TOBASE BATCH) Compound CA Ex. 1 Ex. 2 Ex. 3 CB Ex. 4 Ex. 5 CC Ex. 6 Ex. 7Ex. 8 Fe₂O_(3:) 0.102 0.102 0.102 0.102 0.09 0.09 0.09 0.033 0.033 0.0330.033 Er₂O_(3:) 0 0.06 0.08 0.11 0 0.086 0.08 0 0 0.10 0.09 CeO_(2:) 00.035 0.035 0.035 0 0.066 0.06 0 0.08 0.10 0.09 Nd₂O_(3:) 0 0 0 0 0 0 00.02 0.02 0.03 0.025

[0040] The batches were melted and glass formed using known techniques.Solar characteristics for the resulting Example glasses were as followsin the table below, with the below measurements taken after the melt andformation of the glass. It is noted that Lta (visible transmission %),UV transmission %, and % TS were measured using Ill. C, 2 degreeobserver, while transmissive L*, a* and b* color coordinates (CIE) weremeasured using Ill. D65, 10 degree observer. Moreover, Dom. X stands fordominant wavelength, and Pe stands for excitation purity. All glasssamples were about 0.219 inches thick (about 5.5-5.6 mm thick).CHARACTERISTICS OF EXAMPLES 1-8 GLASSES Character- istic CA Ex. 1 Ex. 2Ex. 3 CB Ex. 4 Ex. 5 CC Ex. 6 Ex. 7 Ex. 8 % Lta 88.4 88.0 87.7 86.2 88.889.7 89.4 88.0 89.6 89.0 88.5 % UV 74.5 68.9 74.8 73.6 76.9 65.9 66.476.2 65.9 63.2 63.6 % TS 79.6 83.1 81.3 79.8 79.2 84.5 84.0 79.5 84.986.0 84.9 FeO (wt. %) .0232 .011 .0177 .0191 .0254 .009 .0104 .023 .0079.0042 .0065 Dom. λ (nm) 498 562 487 487 493 573 564 492 537 566 581 Pe %0.64 0.37 0.24 0.22 0.9 0.48 0.27 0.96 0.25 0.07 0.07 L* 95.5 95.2 95.194.4 95.7 95.8 95.7 93.6 95.9 95.6 95.4 a* −1.54 −0.34 −0.18 −0.15 −1.49−0.1 −0.21 −1.41 −0.72 0.09 −0.05 b* 0.24 0.51 −0.12 −0.11 −0.15 0.580.39 −0.29 0.47 0.11 0.14

[0041] It can be seen from the above that glasses according to differentembodiments of this invention (Examples 1-8) have one or more of thefollowing example advantages over the Comparative Examples (CA, CB, andCC): (i) glasses according to Examples 1-8 had more neutral color thanthe respective Comparative Examples CA, CB and CC (it is noted that theComparative Examples did not include erbium or cerium); (ii) glassesaccording to Examples 1-8 had less FeO (i.e., less iron in the ferrousstate) than the respective examples (CA, CB and CC), even though therespective Examples and Comparative Examples for comparing therewith hadthe same amount of total iron; and/or (iii) glasses according toExamples 1-8 had lower excitation purity (Pe) than the respectiveComparative Examples CA, CB and CC. High visible transmission (Lta) wasmaintained in Examples 1-8.

[0042] With respect to color, it can be seen for example that Example 1was characterized by much more neutral a* color than CA (i.e., a* wascloser to zero in Example 1 than in CA); compare a*=−0.34 of Example 1with a*=−1.54 of Comparative Example A (CA). In a similar manner, it canbe seen for example that Example 4 had much more neutral a* color thanCB (i.e., a* was closer to zero in Example 4 than in CB); comparea*=−0.1 of Example 4 with a*=−1.49 of Comparative Example B (CB). In asimilar manner, it can be seen for example that Example 7 had much moreneutral a* color than CC (i.e., a* closer to zero in Example 7 than inCC); compare a*=0.09 of Example 7 with a*=−1.41 of Comparative Example C(CC). The improved neutral color of example embodiments of thisinvention is a result of the unique material combinations used inglasses according to example embodiments of this invention.

[0043] It is noted that in any of Examples 1-8 above, the cerium oxidemay be replaced with sodium nitrate in certain embodiments of thisinvention (see amounts in Tables 4-6 above). Certain examples accordingto other embodiments of this invention are set forth below (same baseglass as above for other examples), where Examples 10-11 utilize sodiumnitrate was used instead of or in addition to cerium oxide. It is notedthat Examples 9-11 differed from Examples 1-8 above in that for Examples9-11 each glass sample was only 0.161 inches thick. BATCH MATERIALS INEXAMPLES 9-11 (IN ADDITION TO BASE BATCH) Compound Ex. 9 Ex. 10 Ex. 11Fe₂O_(3:) 0.054 0.055 0.048 Er₂O_(3:) 0.06 0 0 CeO_(2:) 0.06 0.09 0NaNO_(3:) 0 0.5 0.78 Nd₂O_(3:) 0 0 0

[0044] The above batches were melted and glass formed using knowntechniques. Solar characteristics for the resulting Example glasses wereas follows in the table below, with the below measurements taken afterthe melt and formation of the glass. CHARACTERISTICS OF EXAMPLES 9-11GLASSES Characteristic Ex. 9 Ex. 10 Ex. 11 % Lta 90.43 91.32 90.75 % UV71.81 72.63 77.73 % TS 87.78 90.54 88.14 FeO (wt. %) 0.0031 0.00070.0048 Dom. λ(nm) 578 570 566 Pe % 0.63 0.41 0.53 L* 96.11 96.52 96.29a* 0.09 −0.18 −0.36 b* 0.67 0.5 0.67

[0045] As with the previous examples, it can be seen that Examples 9-11have improved color (more neutral) and high visible transmissionrelative to the comparative examples, albeit reduced thickness. It isnoted that Examples 9-11 utilized a smaller amount of total iron thanExamples 1-8. Examples 9-11 illustrate that according to certain exampleembodiments of this invention, the glass may even have a visibletransmission of at least 90% when at a reference thickness of about0.161 inches.

[0046] The terms, and characteristics, of ultraviolet lighttransmittance (% UV), dominant wavelength, and excitation purity (i.e. %“purity”, or Pe) are well understood terms in the art, as are theirmeasurement techniques. Such terms are used herein, in accordance withtheir well known meaning, e.g., see U.S. Pat. No. 5,308,805. Inparticular, ultraviolet transmittance (% UV) is measured herein usingParry Moon Air Mass=2 (300-400 nm inclusive, integrated using Simpson'sRule at 10 nm intervals). Dominant wavelength (DW) is calculated andmeasured conventionally in accord with the aforesaid CIE Publication15.2 (1986) and ASTM: E 308-90. The term “dominant wavelength” includesboth the actual measured wavelength and, where applicable, itscalculated complement. Excitation purity (Pe or % “purity”) is measuredconventionally in accordance with CIE Publication 15.2 (1986) and ASTM:E 308-90.

[0047] Once given the above disclosure many other features,modifications and improvements will become apparent to the skilledartisan. Such features, modifications and improvements are thereforeconsidered to be a part of this invention, the scope of which is to bedetermined by the following claims:

What is claimed is:
 1. Glass comprising: Ingredient wt. % SiO₂ 67-75%Na₂O 10-20% CaO  5-15% MgO  0-5% Al₂O₃  0-5% K₂O  0-5% total iron(expressed as Fe₂O₃)  0.01 to 0.30% erbium oxide  0.01 to 0.30% ceriumoxide 0.005 to 0.30%

wherein the glass has visible transmission of at least 75% , atransmissive a* color value of −1.0 to +1.0, and a transmissive b* colorvalue of −1.0 to +1.5.
 2. The glass of claim 1, wherein the glasscomprises: total iron (expressed as Fe₂O₃) 0.02 to 0.20% erbium oxide0.02 to 0.20% cerium oxide 0.01 to 0.18%.


3. The glass of claim 2, wherein the glass comprises: total iron(expressed as Fe₂O₃) 0.03 to 0.15% erbium oxide 0.03 to 0.13% ceriumoxide 0.03 to 0.12%.


4. The glass of claim 1, wherein the glass further comprises from 0.005to 0.15% neodymium oxide.
 5. The glass of claim 4, wherein the glassfurther comprises from 0.010 to 0.050% neodymium oxide.
 6. The glass ofclaim 1, wherein the glass has a redox value (FeO/Fe₂O₃)←0.20.
 7. Theglass of claim 1, wherein the glass has a redox value (FeO/Fe₂O₃)←0.15.8. The glass of claim 1, wherein the glass has a redox value(FeO/Fe₂O₃)←0.13.
 9. The glass of claim 1, wherein the glass furthercomprises less than or equal to 0.020% FeO.
 10. The glass of claim 1,wherein the glass further comprises less than or equal to 0.015% FeO.11. The glass of claim 1, wherein the glass further comprises less thanor equal to 0.011% FeO.
 12. The glass of claim 1, wherein the glass hasa visible transmission of at least 80%.
 13. The glass of claim 1,wherein the glass has a visible transmission of at least 85%.
 14. Amethod of making glass, the method comprising: providing a glass batchcomprising: Ingredient wt. % SiO₂ 67-75% Na₂O 10-20% CaO  5-15% MgO 0-5% Al₂O₃  0-5% K₂O  0-5% total iron (expressed as Fe₂O₃)  0.01 to0.30% erbium oxide  0.01 to 0.30% cerium oxide and/or a nitrate 0.005 to2.0% neodymium oxide    0 to 0.15%

melting the batch and forming a resulting glass that has visibletransmission of at least 75%, a transmissive a* color value of −1.0 to+1.0, and a transmissive b* color value of −1.0 to +1.5.
 15. The methodof claim 14, wherein the nitrate comprises at last one of potassiumnitrate (KNO₃) and sodium nitrate (NaNO₃), and the batch comprises:total iron (expressed as Fe₂O₃) 0.02 to 0.20% erbium oxide 0.02 to 0.20%cerium oxide 0.01 to 0.18% neodymium oxide   0 to 0.15%.


16. The method of claim 14, wherein the glass has a redox value(FeO/Fe₂O₃)←0.20.
 17. The method of claim 14, wherein the glass has aredox value (FeO/Fe₂O₃)←0.15.
 18. The method of claim 14, wherein theglass has a redox value (FeO/Fe₂O₃)←0.13.
 19. The method of claim 14,wherein after the melting the glass comprises less than or equal to0.020% FeO.
 20. The method of claim 19, wherein the glass comprises lessthan or equal to 0.015% FeO.
 21. The method of claim 20, wherein theglass comprises less than or equal to 0.011% FeO.
 22. The method ofclaim 14, wherein the glass has a visible transmission of at least 80%.23. Glass comprising: total iron (expressed as Fe₂O₃)  0.01 to 0.30%erbium oxide  0.01 to 0.30% cerium oxide 0.005 to 0.30%.


24. The glass of claim 23, wherein the glass has visible transmission ofat least 75%, a transmissive a* color value of −1.0 to +1.0, and atransmissive b* color value of −1.0 to +1.5.
 25. The glass of claim 23,wherein the glass comprises: total iron (expressed as Fe₂O₃) 0.02 to0.20% erbium oxide 0.02 to 0.20% cerium oxide 0.01 to 0.18%.


26. The glass of claim 23, wherein the glass comprises: total iron(expressed as Fe₂O₃) 0.03 to 0.15% erbium oxide 0.03 to 0.13% ceriumoxide 0.03 to 0.12%.


27. The glass of claim 23, wherein the glass further comprises from0.005 to 0.15% neodymium oxide.
 28. The glass of claim 23, wherein theglass has a redox value (FeO/Fe₂O₃)←0.15.
 29. The glass of claim 23,wherein the glass has a redox value (FeO/Fe₂O₃)←0.13.
 30. The glass ofclaim 23, wherein the glass further comprises less than or equal to0.015% FeO.
 31. The glass of claim 23, wherein the glass has a visibletransmission of at least 85%.
 32. A method of making glass, the methodcomprising providing a glass batch comprising: total iron (expressed asFe₂O₃):  0.01 to 0.30% erbium oxide:  0.01 to 0.30% cerium oxide and/ora nitrate: 0.005 to 2.0%, and using the glass batch to make glass.


33. The method of claim 32, wherein the batch comprises a nitrate in theamount (wt. %) of from 0.005 to 2.0%.
 34. The method of claim 33,wherein the nitrate comprises at least one of potassium nitrate (KINO₃)and sodium nitrate (NaNO₃).
 35. The method of claim 34, wherein thebatch comprises at least one of potassium, nitrate (KNO₃) and sodiumnitrate (NaNO₃) in a total amount of from 0.2 to 1.5%.
 36. The method ofclaim 32, wherein the glass has visible transmission of at least 75%, atransmissive a* color value of −1.0 to +1.0, and a transmissive b* colorvalue of −1.0 to +1.5.
 37. The method of claim 32, wherein the glasscomprises: total iron (expressed as Fe₂O₃) 0.02 to 0.20% erbium oxide0.02 to 0.20% cerium oxide 0.01 to 0.18%.


38. The method of claim 32, wherein the glass comprises: total iron(expressed as Fe₂O₃) 0.02 to 0.20% erbium oxide 0.02 to 0.20% neodymiumoxide   0 to 0.15%.


39. The method of claim 32, wherein glass comprises from 0.005 to
 0. 15%neodymium oxide.
 40. The method of claim 32, wherein the glass has aredox value (FeO/Fe₂O₃)←0.15.
 41. The method of claim 32, wherein theglass has a redox value (FeO/Fe₂O₃)←0.13.
 42. The method of claim 32,wherein the glass further comprises less than or equal to 0.015% FeO.43. The method of claim 32, wherein the glass has a visible transmissionof at least 85%.
 44. Glass comprising: total iron (expressed as Fe₂O₃)0.01 to 0.30% erbium oxide 0.01 to 0.30%.


45. The glass of claim 44, further comprising: total iron (expressed asFe₂O₃) 0.02 to 0.20% erbium oxide 0.02 to 0.20%.


46. The glass of claim 44, further comprising: total iron (expressed asFe₂O₃) 0.03 to 0.15% erbium oxide 0.03 to 0.13%.


47. The glass of claim 44, further comprising from 0.005 to 0.15%neodymium oxide.
 48. The glass of claim 44, further comprising from0.010 to 0.050% neodymium oxide.
 49. The glass of claim 44, furthercomprising from 0.005 to 0.30% cerium oxide.
 50. The glass of claim 44,wherein the glass has visible transmission of at least 75%, atransmissive a* color value of −1.0 to +1.0, and a transmissive b* colorvalue of −1.0 to +1.5.
 51. The glass of claim 50, wherein the glass hasa visible transmission of at least 85%.
 52. The glass of claim 44,wherein the glass has a redox value (FeO/Fe₂O₃)←0.15.
 53. The glass ofclaim 44, wherein the glass has a redox value (FeO/Fe₂O₃)←0.13.
 54. Theglass of claim 44, wherein the glass further comprises less than orequal to 0.015% FeO.
 55. The glass of claim 44, further comprising: SiO₂67-75% Na₂O 10-20% CaO  5-15% MgO  0-5% Al₂O₃  0-5% K₂O  0-5%.


56. Glass comprising: neodymium oxide 0.005 to 0.15%, and erbium oxide 0.01 to 0.30%.


57. The glass of claim 56, further comprising: total iron (expressed asFe₂O₃) 0.02 to 0.20% erbium oxide 0.02 to 0.20%.


58. The glass of claim 56, further comprising from 0.005 to 0.30% ceriumoxide.
 59. The glass of claim 56, wherein the glass has visibletransmission of at least 75%.
 60. The glass of claim 59, wherein theglass has a transmissive a* color value of −1.0 to +1.0, and atransmissive b* color value of −1.0 to +1.5.
 61. The glass of claim 56,wherein the glass has a visible transmission of at least 85%.
 62. Theglass of claim 57, wherein the glass has a redox value (FeO/Fe₂O₃)←0.15.63. Glass comprising: total iron (expressed as Fe₂O₃)  0.01 to 0.30%neodymium oxide 0.005 to 0.15%.


64. The glass of claim 63, further comprising total iron (expressed asFe₂O₃) 0.02 to 0.20% erbium oxide 0.02 to 0.20%.


65. The glass of claim 63, further comprising from 0.005 to 0.30% ceriumoxide.
 66. The glass of claim 63, wherein the glass has visibletransmission of at least 75%, a transmissive a* color value of −1.0 to+1.0, and a transmissive b* color value of −1.0 to +1.5.
 67. The glassof claim 63, wherein the glass has a visible transmission of at least85%.
 68. The glass of claim 63, wherein the glass has a redox value(FeO/Fe₂O₃)←0.15.
 69. The glass of claim 63, wherein the glass furthercomprises less than or equal to 0.015% FeO.
 70. The glass of claim 63,further comprising: SiO₂ 67-75% Na₂O 10-20% CaO  5-15% MgO  0-5% Al₂O₃ 0-5% K₂O  0-5%.


71. The glass of claim 1, wherein the glass has a visible transmissionof at least 90% when having a reference thickness of from 5.5 to 5.6 mm.72. The glass of claim 23, wherein the glass has a visible transmissionof at least 90% when having a reference thickness of from 5.5 to 5.6 mm.73. The glass of claim 44, wherein the glass has a visible transmissionof at least 90% when having a reference thickness of from 5.5 to 5.6 mm.74. Glass comprising: total iron (expressed as Fe₂O₃) 0.01 to 0.10%cerium oxide 0.01 to 0.18%

wherein the glass has a visible transmission of at least 85%, atransmissive a* color value of −1.0 to +1.0, and a transmissive b* colorvalue of −1.0 to +1.5.
 75. The glass of claim 74, wherein the glass hasa redox value (FeO/Fe₂O₃)←0.15.
 76. The glass of claim 74, furthercomprising from 0.02 to 0.20% erbium oxide.
 77. The glass of claim 74,wherein the glass was made using a batch comprising from 0.005 to 2.0%of nitrate.
 78. The glass of claim 77, wherein the nitrate comprisesNaNO₃.